Aims. We investigate the temporal evolution of magnetic flux emerging
within a granule in the quiet-Sun internetwork at disk center.

Methods. We combined IR spectropolarimetry of high angular resolution performed
in two Fe i lines at 1565 nm with speckle-reconstructed G-band
imaging. We determined the magnetic field parameters by a LTE inversion
of the full Stokes vector using the SIR code, and followed their evolution
in time. To interpret the observations, we created a geometrical model
of a rising loop in 3D. The relevant parameters of the loop were matched
to the observations where possible. We then synthesized spectra from the
3D model for a comparison to the observations.

Results. We found signatures of magnetic flux emergence within a growing granule.
In the early phases, a horizontal magnetic field with a distinct
linear polarization signal dominated the emerging flux. Later on, two
patches of opposite circular polarization signal appeared symmetrically
on either side of the linear polarization patch, indicating a small
loop-like structure. The mean magnetic flux density of this loop was
roughly 450 G, with a total magnetic flux of around 3 1017 Mx.
During the ~12 min episode of loop occurrence, the spatial extent
of the loop increased from about 1 to 2 arcsec. The middle part of the
appearing feature was blueshifted during its occurrence, supporting the
scenario of an emerging loop. There is also clear evidence for the interaction
of one loop footpoint with a preexisting magnetic structure of opposite
polarity. The temporal evolution of the observed spectra is reproduced to first order by the spectra derived from the geometrical model. During the phase of clearest visibility of the loop in the observations, the observed and synthetic spectra match quantitatively.

Conclusions. The observed event can be explained as a case of flux emergence in the
shape of a small-scale loop. The fast disappearance of the loop at the
end could possibly be due to magnetic reconnection.

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